1. Field of the Invention (Technical Field)
The present invention relates to optical switches, particularly to the use of voice coil motor based computer disk drive assembly technology to align input and output optical channels.
2. Background Art
Present day optical fiber technologies are revolutionizing the telecommunications industry. Tremendous advances have been made in the field of telecommunications over the past decade. It has been estimated that this technology is capable of carrying tens of millions of conversations simultaneously on a single optical fiber. Optical fiber communication systems offer many advantages over systems that use copper wire or radio frequency links as transmission media. They include lower transmission losses, higher bandwidths, higher transmission rates, lower implementation costs, greater reliability and greater electrical isolation characteristics. It is clear that optical fiber communication will dominate the telecommunications industry in the very near future because of advantages such as these.
Fiber optic switching is an important component in any telecommunication system. These systems use switches to establish communication channels among two or more of their interfaces. An optical fiber switch is capable of optically connecting, interrupting or aligning, any one or more of a first group of optical fibers with any one or more of a second group of optical fibers, or vice versa, enabling an optical signal to propagate through the optical interface junction between newly aligned fibers.
When two optical fibers are aligned end-to-end, light entering one fiber (the input or sending fiber) will continue into and through the second fiber (the output or receiving fiber) while the two adjacent ends, or faces, are aligned and close together. Fiber optic switches misalign or disjoin the adjacent ends of the fibers by moving one or both of the two ends. By moving, for example, the first fiber""s end to a new location, the signal, in this case light, can be redirected into a third fiber by aligning the first fiber""s end with an end of the third fiber.
Lateral separation of two adjacent fiber ends will result in loss of light between the two fibers and a light absorber is typically provided beside the fiber which either moves into place as the receiving fiber moves away or stays in place as the sending fiber moves away. Space is provided for this motion. This effectively switches the signal off. The discontinuity between the fiber ends may be either perpendicular to the fiber axis or at some angle to the axis but the gap is minimal when the fibers are aligned.
Fibers are often collected into a bundle, a fiber optic cable, with a structure set up at the active location to permit the required motion of a fiber end. A fiber bundle can be separated from a circular bundle cross-section to a linear arrangement where the fibers are in a straight line at the switch but reformed into a bundle again at the device exit.
Optical fiber switches may include electronic processing as part of signal transmission. Switches wherein the signal is entirely optical while being transmitted, such as the present invention, are described as photonic. Optical fiber switches, which are totally photonic, generally utilize fiber positioning means, alignment signal emitter means and computer control means. Some switching concepts, not utilized in the present invention, may include light beams and lenses. Normally, a fiber positioning means is provided near the end of one fiber to selectively point the end of that fiber in one fiber group toward the end of another fiber in the other fiber group to perform a switched optical transmission. Patents proposing to perform such switching actions in fiber optic telecommunication systems include: U.S. Pat. No. 5,024,497, to Jebens, entitled xe2x80x9cShape Memory Alloy Optical Fiber Switch,xe2x80x9d which discusses switching activated by a shape memory alloy wire in a transverse direction. U.S. Pat. No. 4,512,036, entitled xe2x80x9cPiezoelectric Apparatus for Positioning Optical Fibers,xe2x80x9d U.S. Pat. No. 4,543,663, entitled xe2x80x9cPiezoelectric Apparatus for Positioning Optical Fibers,xe2x80x9d U.S. Pat. No. 4,651,343, entitled xe2x80x9cPiezoelectric Apparatus for Positioning Optical Fibers,xe2x80x9d and U.S. Pat. No. 5,524,153, entitled xe2x80x9cOptical Fiber Switching System and Method Using Same,xe2x80x9d all to Laor, use piezoelectric bimorphs for positioning optical fiber switches. U.S. Pat. No. 4,303,302, to Ramsey, et al., entitled xe2x80x9cPiezoelectric Optical Switchxe2x80x9d discusses other forms of piezoelectric bimorphs for optical fiber switching.
Other patents discussing fiber optic switching include: U.S. Pat. No. 5,812,711, to Glass, et al., entitled xe2x80x9cMagnetostrictively Tunable Optical Fiber Gratingsxe2x80x9d; U.S. Pat. No. 5,812,711 to Malcolm, et al., entitled xe2x80x9cMagnetostrictive Tunable Optical-Fiber Gratingsxe2x80x9d; U.S. Pat. No. 4,759,597, to Lamonde, entitled xe2x80x9cMechanical Switch for Optical Fibersxe2x80x9d; U.S. Pat. No. 4,415,228, to Stanley, entitled xe2x80x9cOptical Fiber Switch Apparatusxe2x80x9d; U.S. Pat. No. 5,004,318, to Ohashi, entitled xe2x80x9cSmall Optical Fiber Switchxe2x80x9d; U.S. Pat. No. 4,844,577, to Ninnis, et al, entitled xe2x80x9cBimorph Electro Optic Light Modulatorxe2x80x9d; U.S. Pat. No. 4,512,627, to Archer, et al., entitled xe2x80x9cOptical Fiber Switch, Electromagnetic Actuating Apparatus with Permanent Magnet Latch Controlxe2x80x9d; U.S. Pat. No. 5,699,463, to Yang, et al., entitled xe2x80x9cMechanical Fiber Optic Switchxe2x80x9d; U.S. Pat. No. 5,841,912, to Mueller-Fiedler, entitled xe2x80x9cOptical Switching Devicexe2x80x9d; U.S. Pat. No. 5,647,033, to Laughlin entitled xe2x80x9cApparatus for Switching Optical Signals and Method of Operationxe2x80x9d; U.S. Pat. No. 4,886,335, to Yanagawa, et al., entitled xe2x80x9cOptical Fiber Switch Systemxe2x80x9d; and U.S. Pat. No. 4,223,987, to Kummer, et al., entitled xe2x80x9cMechanical Optical Fiber Switching Device.xe2x80x9d These patents disclose various methods for fiber optic switching, including mechanical devices such as rods, motors, and adapters, as well as wave guides and reflectors.
The present invention overcomes deficiencies in the prior art and provides fast and accurate optical switching. A modified conventional computer disk drive is used to move optical fibers over distances of a few centimeters with an access time of a few milliseconds. A group of fibers are input through and held by the actuator arm, or head, assembly of the computer disk drive and movement of the actuator arm then aligns/misaligns the input fibers with selected output fibers that are placed through and held by the disk of the disk drive. Additionally the disk is partially rotatable, and the combined movement of the actuator arm and the disk increases the switching speed. A conventional computer disk drive with a high resolution voice coil motor is used to achieve positional resolution on the order of 0.5 micron.
The present invention is an optical switch comprising at least one actuator arm for fixedly holding at least one input optical channel, and a disk for fixedly holding at least one output optical channel, wherein at least one of the actuator arm and disk are movable with respect to the others so that the at least one input optical channel is aligned with selected of the at least one output optical channel. The actuator arm comprises at least one opening for fixedly holding at least one output end of the at least one input optical channels. The disk also comprises at least one opening for fixedly holding at least one input end of the at least one output optical channel.
A voice coil motor is used for receiving a switching signal to cause each actuator arm to move with respect to the disk. The voice coil motor can be a linear voice coil motor if the actuator arm is a linear actuator arm. Otherwise the actuator arm is pivotable. Preferably the voice coil motor comprises a high resolution voice coil motor providing a positional resolution of between approximately 0.25 and 1 micron. The optical switch further comprises fixed supports for stabilizing the input and output optical channels. The disk of the optical switch preferably comprises a partially rotatable disk. Alternatively, the disk of the optical switch comprises a linearly movable disk that operates in conjunction with a linear actuator arm that is controlled by a linear voice coil motor.
The present invention is also a method of optical switching comprising the steps of providing a disk drive assembly; fixedly holding at least one input optical channel with at least one actuator arm of the disk drive assembly; fixedly holding at least one output optical channel with the disk of the disk drive assembly; moving at least one of the at least one actuator arm and disk with respect to the others; and aligning the at least one input optical channel with the selected at least one output optical channel. The step of fixedly holding at least one input optical channel with at least one actuator arm comprises providing at least one opening in the actuator arm for fixedly holding at least one output end of the at least one input optical channel. Fixedly holding at least one output optical channel with the disk of the disk drive assembly comprises providing at least one opening in the disk for fixedly holding at least one input end of the at least one output optical channel.
The method further comprises the step of receiving a switching signal with at least one voice coil motor and thereby moving the at least one actuator arm. Receiving a switching signal with at least one voice coil motor can comprise receiving a switching signal with at least one linear voice coil motor, when the actuator arm is a linear actuator arm. The method of optical switching further comprises the step of achieving a positional accuracy of between approximately 0.25 and 1 micron when aligning the input and output optical channels.
The step of moving at least one of the at least one actuator arm and disk with respect to the other can comprise pivoting at least one pivotable actuator arm with respect to the disk. Alternatively, moving at least one of the actuator arm and disk with respect to the others comprises linearly moving at least one linear actuator arm with respect to the disk. The method can further comprise the steps of stabilizing the at least one input optical channel with a fixed support and stabilizing the at least one output optical channel with a fixed support. Moving at least one of the at least one actuator arm and disk with respect to the others can comprise partially rotating a partially rotatable disk with respect to the at least one actuator arm. Alternatively, moving at least one of the at least one actuator arm and disk with respect to the others comprises linearly moving a linearly movable disk with respect to the at least one actuator arm.
The present invention is further an actuator arm optical switch comprising at least two actuator arms for fixedly holding at least one input optical channel and at least one output optical channel, wherein at least one of said actuator arms is movable with respect to the others so that the at least one input optical channel is aligned with the selected at least one output optical channel. At least one of the actuator arms comprises at least one opening for fixedly holding at least one output end of the at least one input optical channel. The remainder of the actuator arms comprise at least one opening for fixedly holding at least one input end of said at least one output optical channel. The optical switch further comprises at least one voice coil motor capable of receiving a switching signal and causing the at least one actuator arm to pivot. Preferably the voice coil motor comprises a high resolution voice coil motor providing a positional resolution of between approximately 0.25 micron and 1 micron. The optical switch preferably further comprises fixed supports for stabilizing the at least one input optical channel and the at least one output optical channel.
The present invention is further a method of optical switching comprising the steps of providing at least two actuator arms; fixedly holding at least one input optical channel with at least one actuator arm; fixedly holding at least one output optical channel with the remainder of the actuator arms; moving at least one of the actuator arms with respect to the others; and aligning the at least one input optical channel with the selected at least one output optical channel. Fixedly holding at least one input optical channel with at least one actuator arm comprises providing at least one opening in the actuator arm for fixedly holding at least one output end of the at least one input optical channel. The step of fixedly holding at least one output optical channel with the remainder of the actuator arms comprises providing at least one opening in the remainder of the actuator arms for fixedly holding at least one input end of the at least one output optical channel.
The method further comprises the step of receiving a switching signal with at least one voice coil motor and thereby pivoting at least one of the actuator arms. The method also further comprises achieving a positional accuracy of between approximately 0.25 and 1 micron when aligning the input and output optical channels. The method of optical switching also comprises the steps of stabilizing the at least one input optical channel with a fixed support and stabilizing the at least one output optical channel with a fixed support.
A primary object of the present invention is to provide an accurate optical switch that quickly aligns input optical fibers with selected output optical fibers using a modified conventional computer disk drive assembly with a high resolution voice coil motor.
A primary advantage of the present invention is that it uses commercially available computer disk drive assemblies to provide positional alignment accuracy of between approximately 0.25 and 1 micron. As a consequence especially due to the end-to-end placement of input and output fibers, the present invention is less expensive, more reliable, longer-lived, rapid acting, more amenable to design variation and more compatible with different system requirements than the prior art.
Another advantage of the present invention is that no collimating lenses are needed because the fibers align in close proximity to each other, end-to-end, with only a fraction of a micron misalignment. The tight connection minimizes transmission losses.
Yet another advantage of the present invention is that it benefits from the fast access time of typical computer disk drives on the order of a few milliseconds.
Still another advantage of the present invention is that it utilizes the well-established body of associated conventional and commercially available hardware and software to drive and control the disk drive optical switch.
Still yet another advantage of the present invention is that, in contrast to prior art switches that employ micro-mirrors or lenses to bounce light off of optical fibers, no micro-mirrors or lenses are used in the present invention.
Other objects, advantages and novel features, and further scope of applicability of the present invention will be set forth in part in the detailed description to follow, taken in conjunction with the accompanying drawings, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.